Population structure, density and biomass of the Eastern

Population structure, density and biomass of the Eastern

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Population structure, density and
biomass of the Eastern oyster on
a novel modular artificial oyster reef
in Chesapeake Bay
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Russell P. Burke* and Romuald N. Lipcius
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Virginia Institute of Marine Science,
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The College of William and Mary
Gloucester Point, Virginia, USA
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Steamer Rock
Modular Reef
System
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Module Schematic
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Modules Prior to Deployment
Before: October 2000
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After: 27 May 2005
Diverse Reef Community:
Community: oysters, mussels, mud crabs,
gobies, blennies, oystertoads,
oystertoads, worms, sponges, barnacles,
anemones, tunicates, iso/amphipods,
iso/amphipods, and potentially larger
mobile predatory species
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Hole
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Bottom
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Top
Red Beard Sponge
Side
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Area (m2)
Area (m2)
3.1
Side
Hole
2.9
5.7
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Face
Top
3.1
14.8
td
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Bottom
Total/Module
74.2
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Reef Total
The Point: Sediment Surface Area = ~5 square meters
5 modules equates to ~15x more surface area
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Results
Per m2 of Bottom
Oyster Density
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Sampling Results
Surface Area
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7.2 m2
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# of Mussels
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523
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# of Oysters
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4281
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Bivalve Volume
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40.33 L
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Sponge Volume
13.58 L
1085
Mussel Density
8617
Oyster Biomass*
1.643 kg
Mussel Biomass*
0.666 kg
*Biomass derived from
Tissue Dry Mass
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Size Structure of Oysters
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Histogram of Height/Length_Oyster (L) - 120 Samples
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Frequency
20
0
17.5
35.0
52.5
70.0
87.5
105.0
Height/Length_Oyster (L)
122.5
140.0
Spat
Small
Market
Discharge/10
Rappahannock River Flow
& Oyster Density v. Year
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400
Poor Recruitment
Good Recruitment
GoodRe
cruitment Low Disease Stress
Elevated Disease
Stress
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300
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200
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100
0
1999
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3
-1
Live Oysters m ; Discharge/10 (ft s )
500
2000
2001
2002
Year
2003
2004
2005
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Size Structure of Oysters
2002
2001
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2003
10
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15
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Frequency
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2004
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Histogram of Height/Length_Oyster (L) - 120 Samples
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35.0
52.5
70.0
87.5
105.0
Height/Length_Oyster (L)
122.5
140.0
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17.5
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5
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The 2003 and 2004 year classes were smaller than the 2001 and 2002
year classes which may explain modes of similar height.
Also, the lower disease stress of 2003 and 2004 would allow for the 2001
and 2002 year classes to continue to grow without the typical adult-onset
mortality.
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Histogram of Height/Length_Mussel (L)
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Size Structure of Mussels
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30
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Frequency
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20
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10
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22.5
30.0
37.5
45.0
Height/Length_Mussel (L)
52.5
60.0
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15.0
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For a bivalve that is not stressed and has had just over four years to
establish a barren habitat, this is a distribution one might expect.
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Oyster Abundance
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1800
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1400
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1200
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1000
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m
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800
600
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0
– Significant Layer
and Face Effects
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200
Top
Side
Hole
Face
– Non-significant
Layer effect
– Significant Face
Effect:
Top > Bottom =
Hole = Side
Mussel Density
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400
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Oyster Total for Top 3 modules
1600
Two-Way ANOVAs:
Oyster Density
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Oyster Total for Top 3 Modules v. Face
Bottom
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Facilitation of Oysters & Mussels?
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Scatterplot of Live Oysters vs Live Mussels
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5
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Live Oysters
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20
20
40
60
80
100
Live Mussels
120
140
160
180
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Modular Reef System
Potentially four distinct oyster year classes that have
fostered a diverse reef community
2.
High oyster (1085) & mussel (8617) density (# m-2 of
bottom); comparable to the best restored reefs in the
Chesapeake Bay (i.e. Fisherman’s Island)
3.
High oyster (1.643 kg) & mussel (0.666 kg) biomass
4.
Significant Face effect; no Module Layer effect
5.
Potential density-mediated facilitation (low-med) and
competition (high) between oysters and mussels
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Bottom
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Top
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Side
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Red Beard Sponge
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Note the
Thickness
of Growth
on this
Concrete
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Hole
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Results
Mussel
Oyster
Mussel
Module:
Density*
Density*
Abundance**
Abundance**
5-Top
73
528
4-Middle
76
766
3-Bottom
71
447
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Oyster
7833
1123
11362
1052
6635
1660
494
5158
145
113
418
493
313
2823
24
123
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1079
159
Side
39
Hole
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Top
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Face:
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Bottom
40
*Density (per m2 of concrete surface); **Abundance (# of individuals)
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Extrapolating Over Whole Reef
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Estimate using
dry mass (kg)
7.293
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Oyster Biomass
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Estimate using
density (#/m2)
---------
6.207
5424
5350
43,050
43,806
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Mussel Biomass
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Total # of Oysters
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Total # of Mussels
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Oyster vs. Mussel Density
Scatterplot of Mussel Density vs Oyster Density (no./sq m)
3000
2500
2000
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Mussel Density
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400
1500
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200
1000
500
0
2000
2500
se
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1500
Mussel Density
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1000
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500
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100
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Oyster Density (no./sq m)
500
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Scatterplot of Oyster Density (no./sq m) vs Mussel Density
3000
0
0
100
200
300
Oyster Density (no./sq m)
400
500
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Oysters/Mussels v.
Sponge Volume
Scatterplot of Live Oysters vs Sponge Vol
Scatterplot of Live Mussels vs Sponge Vol
14
160
12
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Live Mussels
120
100
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6
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Live Oysters
10
ho
140
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180
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4
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2
100
200
300
400
500
Sponge Vol
600
700
800
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R-Sq = 5.5%
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Regresson: Live oysters versus Sponge Volume
P = 0.108
NS
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Regression Equation:
Live Oysters = 4.76 - 0.00405 (Sponge Volume)
900
80
60
40
20
0
0
100
200
300
400
500
Sponge Vol
600
700
Regresson: Live mussels versus Sponge Volume
P = 0.018
SIG
R-Sq. = 11.5%
Regression Equation:
Live mussels = 48.8 - 0.0793 (Sponge Volume)
800
900
Oyster Size Structure by Face
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5.0
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Oyster Size Structure by Face
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4.5
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4.0
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3.5
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Spat
Juvenile
e
2.5
in
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1.5
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1.0
0.5
Market
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2.0
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Frequency
3.0
Top
Side
Hole
Face
Bottom
Location
Constructed
Spat
Small
2001
Market
Total Spat
2002
Sm all M ar k e t Total Spat
01
126
53
17
196
Broad Cr. (C)
01
507
0
0
507
Broad Cr. (Hs e )
01
430
4
1
435
Butle rs Hole (C)
01
397
0
0
397
Butle rs Hole (Hs e )
01
662
19
688
Butle rs Hole (WS)
01
170
0
0
170
Stur ge on Bar
01
856
15
0
861
M os quito Pt.
01
552
0
0
552
M os quito Pt.
01
615
20
645
M ill Cr e e k
00
6
0
0
6
113
0
0
Parr otts Rk .
00
3
0
0
3
122
0
0
Drum m ing Gr.
00
0
Te m ple Bay
00
220
0
Fe rr y Pt., Cor rotom an
00
175
3
02
"03
Wick s
"03
0
78
15
87
95
7
189
1
71
176
112
1
289
0
93
316
119
3
438
0
383
191
0
574
10
113
301
185
0
122
391
260
7
368
0
368
201
151
0
220
357
192
0
178
110
9
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331
Sm all M ar k e t Total
13
17
7
37
11
83
4
30
6
40
4
176
0
20
1
21
116
5
121
3
49
9
61
0
8
0
8
2
2
1
5
486
0
24
1
25
2
11
6
19
658
1
30
2
33
0
16
1
17
0
352
0
16
1
17
0
11
1
12
0
549
1
100
5
75
0
16
4
20
0
119
0
34
0
34
0
5
2
7
0
369
0
0
369
1
181
8
190
1
63
8
72
42
0
0
42
0
42
3
45
0
11
8
19
0
10
0
10
0
8
1
9
0
1
0
1
0
6
0
6
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*Provided by Jim Wesson, VMRC
Spat
93
o
Wate r vie w
Sm all M ar k e t Total
0
td
02
LaGr ange Cr .
Spat
2004
209
no
Tow le s Pt.
122
2003
in
at
Broad Cr. (WS)
Sm all M ar k e t Total
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Rappahannock
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2000
Date
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Rappahannock Oyster Survey*
Good Recruitment
Low Disease Stress;
Poor Recruitment